The present invention refers to an aircraft lifting surface and more in particular to its main supporting structure.
An aircraft lifting surface usually comprises a torsion box as its main supporting structure. For example, FIGS. 1a, 1b and 1c show a known horizontal tail plane (HTP) structured by leading edges 11, torsion boxes 13 and trailing edges 15 with control surfaces (flaps, elevators, rudders, etc.).
The structural elements of torsion boxes 13 are upper and lower skins 21, 23 stiffened by longitudinal stringers, a front spar 18, a rear spar 20 and transverse ribs 25 attached to the front and rear spars 18, 20 and to the upper and lower skins 21, 23 in order to keep the torsion box shape and reinforce the load introductions areas linked to the HTP structural arrangement in the aircraft and to the actuators for handling the HTP control surfaces.
The leading edge 11 is the structure responsible for keeping the aerodynamic surface with a torsion box surface, for supporting the static or cyclic structural loads involved and for protecting the torsion box from bird impacts. It is the part of the lifting surface that first contacts the air and the foremost edge of an airfoil section.
The leading edge 11 comprises, on the one side, several ribs 29, called leading edge ribs attached to the front spar 18 of the torsion box 13 and, on the other side, the leading edge cover 27—commonly known as “nose”—attached to the leading edge ribs 29 and to the flanges of the front spar 18 in order to keep the overall aerodynamic shape of the lifting surface. Leading edges further comprising additional elements like spars, vertical stiffeners and sandwich cores are also known in the art.
Similarly the trailing edge 15 comprises, on the one side, several ribs, called trailing edge ribs attached to the rear spar 20 of the torsion box 13 and, on the other side, a trailing edge cover 28 attached to the trailing edge ribs and to the flanges of the rear spar 20 or to the edge of the torsion box in order to keep the overall aerodynamic shape of the HTP.
A known assembling method of this HTP comprises the following steps:                Assembling the torsion box 13.        Joining the trailing edge ribs to the torsion box 13.        Joining the trailing edge cover 28 to the torsion box 13 and to the trailing edge ribs.        Joining the leading edge ribs 29 to the torsion box 13.        Joining the leading edge cover 27 to the torsion box 13 and to the leading edge ribs 29.        
Due to the amount of different components to be assembled, the manufacturing of this HTP (and the same applies to other lifting surfaces) is a complex and expensive process and consequently the aeronautics industry is constantly demanding new proposals and new manufacturing methods that improve efficiency, reduce the amount of mechanical joints and reduce costs of aircraft tail planes and other aircraft lifting surfaces.
The present invention is directed to the attention of that demand.